The shorter your sleep, the shorter your life: the new sleep science

Leading neuroscientist Matthew Walker on why sleep deprivation is increasing our risk of cancer, heart attack and Alzheimers and what you can do about it

Matthew Walker has learned to dread the question What do you do? At parties, it signals the end of his evening; thereafter, his new acquaintance will inevitably cling to him like ivy. On an aeroplane, it usually means that while everyone else watches movies or reads a thriller, he will find himself running an hours-long salon for the benefit of passengers and crew alike. Ive begun to lie, he says. Seriously. I just tell people Im a dolphin trainer. Its better for everyone.

Walker is a sleep scientist. To be specific, he is the director of the Center for Human Sleep Science at the University of California, Berkeley, a research institute whose goal possibly unachievable is to understand everything about sleeps impact on us, from birth to death, in sickness and health. No wonder, then, that people long for his counsel. As the line between work and leisure grows ever more blurred, rare is the person who doesnt worry about their sleep. But even as we contemplate the shadows beneath our eyes, most of us dont know the half of it and perhaps this is the real reason he has stopped telling strangers how he makes his living. When Walker talks about sleep he cant, in all conscience, limit himself to whispering comforting nothings about camomile tea and warm baths. Its his conviction that we are in the midst of a catastrophic sleep-loss epidemic, the consequences of which are far graver than any of us could imagine. This situation, he believes, is only likely to change if government gets involved.

Walker has spent the last four and a half years writing Why We Sleep, a complex but urgent book that examines the effects of this epidemic close up, the idea being that once people know of the powerful links between sleep loss and, among other things, Alzheimers disease, cancer, diabetes, obesity and poor mental health, they will try harder to get the recommended eight hours a night (sleep deprivation, amazing as this may sound to Donald Trump types, constitutes anything less than seven hours). But, in the end, the individual can achieve only so much. Walker wants major institutions and law-makers to take up his ideas, too. No aspect of our biology is left unscathed by sleep deprivation, he says. It sinks down into every possible nook and cranny. And yet no one is doing anything about it. Things have to change: in the workplace and our communities, our homes and families. But when did you ever see an NHS poster urging sleep on people? When did a doctor prescribe, not sleeping pills, but sleep itself? It needs to be prioritised, even incentivised. Sleep loss costs the UK economy over 30bn a year in lost revenue, or 2% of GDP. I could double the NHS budget if only they would institute policies to mandate or powerfully encourage sleep.

Why, exactly, are we so sleep-deprived? What has happened over the course of the last 75 years? In 1942, less than 8% of the population was trying to survive on six hours or less sleep a night; in 2017, almost one in two people is. The reasons are seemingly obvious. First, we electrified the night, Walker says. Light is a profound degrader of our sleep. Second, there is the issue of work: not only the porous borders between when you start and finish, but longer commuter times, too. No one wants to give up time with their family or entertainment, so they give up sleep instead. And anxiety plays a part. Were a lonelier, more depressed society. Alcohol and caffeine are more widely available. All these are the enemies of sleep.

But Walker believes, too, that in the developed world sleep is strongly associated with weakness, even shame. We have stigmatised sleep with the label of laziness. We want to seem busy, and one way we express that is by proclaiming how little sleep were getting. Its a badge of honour. When I give lectures, people will wait behind until there is no one around and then tell me quietly: I seem to be one of those people who need eight or nine hours sleep. Its embarrassing to say it in public. They would rather wait 45 minutes for the confessional. Theyre convinced that theyre abnormal, and why wouldnt they be? We chastise people for sleeping what are, after all, only sufficient amounts. We think of them as slothful. No one would look at an infant baby asleep, and say What a lazy baby! We know sleeping is non-negotiable for a baby. But that notion is quickly abandoned [as we grow up]. Humans are the only species that deliberately deprive themselves of sleep for no apparent reason. In case youre wondering, the number of people who can survive on five hours of sleep or less without any impairment, expressed as a percent of the population and rounded to a whole number, is zero.

The world of sleep science is still relatively small. But it is growing exponentially, thanks both to demand (the multifarious and growing pressures caused by the epidemic) and to new technology (such as electrical and magnetic brain stimulators), which enables researchers to have what Walker describes as VIP access to the sleeping brain. Walker, who is 44 and was born in Liverpool, has been in the field for more than 20 years, having published his first research paper at the age of just 21. I would love to tell you that I was fascinated by conscious states from childhood, he says. But in truth, it was accidental. He started out studying for a medical degree in Nottingham. But having discovered that doctoring wasnt for him he was more enthralled by questions than by answers he switched to neuroscience, and after graduation, began a PhD in neurophysiology supported by the Medical Research Council. It was while working on this that he stumbled into the realm of sleep.

Sleep in numbers

Two-thirds of adults in developed nations fail to obtain the nightly eight hours of sleep recommended by the World Health Organisation.

An adult sleeping only 6.75 hours a night would be predicted to live only to their early 60s without medical intervention.

A 2013 study reported that men who slept too little had a sperm count 29% lower than those who regularly get a full and restful nights sleep.

If you drive a car when you have had less than five hours sleep, you are 4.3 times more likely to be involved in a crash. If you drive having had four hours, you are 11.5 times more likely to be involved in an accident.

The time taken to reach physical exhaustion by athletes who obtain anything less than eight hours of sleep, and especially less than six hours, drops by 10-30%.

There are now more than 100 diagnosed sleep disorders, of which insomnia is the mostcommon.

Morning types, who prefer to awake at or around dawn, make up about 40% of the population. Evening types, who prefer to go to bed late and wake up late, account for about 30%. The remaining 30% lie somewhere in between.